Why:
I have multiple display problems in Antergos Gnome and openBox, since a long time. The more then 30 web pages (more then 100 posts), many on the Arch forums, i have already read about this, are not a big help, because mostly outdated and therefor confusing. So, i start this topic to know how to.

Question:
How to setup, step by step, multiple displays properly with the current Antergos version?